1. Field of the Invention
The present disclosure of invention relates to a method of calculating a used time of a light source, a method of displaying lifetime of a light source using the method, and a display apparatus for performing the method. More particularly, example embodiments of the present disclosure relate to a method of calculating a used time of a light source, which is capable of correctly estimating lifetime of a light source, a method of displaying lifetime of a light source using the method, and a display apparatus for performing the method.
2. Description of Related Technology
Generally, the liquid crystal display (LCD) types of flat panel display devices have various advantages, such as reduced thickness of the display panel, lighter weight, lower driving voltages and lower power consumption, etc., as compared to other types of display devices, where the latter include cathode ray tubes (CRTs), plasma display panels (PDPs), etc. As a result, the LCD devices are widely employed for various electronic devices such as desktop computer or TV monitors, laptop computers, cellular telephones, personal digital assistant (PDA) mobile devices, etc.
The typical LCD device includes an LCD panel that displays images by using an electronically-controlled light-transmission valve such as one based on orientation of liquid crystal molecules. The LCD device is basically a non-emissive type display device, so that the LCD device requires a light source such as a backlight device for example to supply a backside of the LCD panel with light.
As the LCD device has become more widely used, including perhaps in mission critical applications, a concern over the useful operational lifetime of the LCD device, and more particularly of its backlighting subunit has also increased. However, the typical LCD device mass production manufacturer can only provide an approximate estimate of lifetime of the LCD device to customers based on laboratory modeling because actual in-field use data is typically not available to the manufacturer.
According to one exemplary method of predicting lifetime of the LCD device, a brightness of lights generated from the backlight unit is measured by using a luminance sensor, and then the remaining lifetime is predicted on the basis of the measured luminance. More specifically, when the measured luminance is found to have decreased to below about 50% of the device's initial luminance, it is determined that the remaining useful lifetime of the backlight unit is finished. If linear degradation is assumed, then loss of half of the useful lifetime of the backlight unit is assumed when the measured luminance is found to have decreased to below about 75% of the device's initial luminance and so on.
Such methods of predicting the remaining useful lifetime of the backlight unit is performed based on an assumption that luminance is a good predictor of the expected lifetime of a light source element which is employed to the backlight unit, so that an approximate half lifetime or other aspect of the backlight unit may be predicted. However, it is difficult to accurately predict remaining useful lifetime of the backlight unit based on luminance alone because many factors can determine lifetime and the assumption of linearity or other trajectory for backlight luminance is not always trustworthy.